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Re: 9i DataGuard, RAC primary - secondary offline for network maintenance

From: Carel-Jan Engel <>
Date: Tue, 05 Dec 2006 23:45:54 +0100
Message-Id: <>

Hi Tony,

See inline
On Tue, 2006-12-05 at 22:09 +0000, Tony Sequeira wrote:

> Hi all,
> I have a 2 node 9i RAC primary (Win 2003), mandated by the
> application.
> Have a physical standby
> All appears to be going well, teething problems over (touch wood).

Cross your fingers. Oracle DOESN'T support DG environments with different versions. It appears you haven't checked the prerequisites carefully enough.

Your standby database is not, mind that you never did a startup migrate and ran catpatch.sql for on the primary. Since your standby is a physical copy of the primary, this database is as well. I don't know why you keep the standby (probably for High Availability reasons), but switching/failing over to it might pop up some surprises. 'Results are unpredictable' is the right phrase here. I cannot emphasize enough that an HA configuration needs SYMMETRY. You're violating this rule#1 here.

> The primary is running in maximum performance mode.
> The secondary server is due to go down for about 24 hours for absolutely
> vital electrical maintenance work.
> I believe that this will be OK, and that the secondary will catch up
> when brought online again.

Yes, no problem. Not that you can use it, effectively it is unavailable as long as you have this mixed version setup running. I have never investigated the combination of a failover/switchover with startup migrate/run catpatch. It might work. Please test it and share your experiences.
There is one big assumption involved in your theory: You have to keep the archived redo log files long enough for the standby to fetch them after it switched on again, As Ric Van Dyke posted while I am writing this.

> Any think or know different? I'm trying to plan for any glitches now,
> the primary database is a vital 24/7 system.

If so, either upgrade your primary to or install at the standby. You don't want surprises at the eve of failover with a vital 24x7 system.

> I am aware of Note:259804.1 - particularly the section 'Real
> Application Clusters and Data Guard Redo Apply During a Network Outage'.

Get aware of , 3rd bullet, too.

Best regards,

Carel-Jan Engel

If you think education is expensive, try ignorance. (Derek Bok) ===

Received on Tue Dec 05 2006 - 16:45:54 CST

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